21957457 has 4 divisors (see below), whose sum is σ = 22204260. Its totient is φ = 21710656.

The previous prime is 21957431. The next prime is 21957473. The reversal of 21957457 is 75475912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1806336 + 20151121 = 1344^2 + 4489^2 .

It is a cyclic number.

It is not a de Polignac number, because 21957457 - 2⁷ = 21957329 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21957757) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123268 + ... + 123445.

It is an arithmetic number, because the mean of its divisors is an integer number (5551065).

Almost surely, 2^21957457 is an apocalyptic number.

It is an amenable number.

21957457 is a deficient number, since it is larger than the sum of its proper divisors (246803).

21957457 is an equidigital number, since it uses as much as digits as its factorization.

21957457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246802.

The product of its digits is 88200, while the sum is 40.

The square root of 21957457 is about 4685.8784662003. The cubic root of 21957457 is about 280.0231996083.

The spelling of 21957457 in words is "twenty-one million, nine hundred fifty-seven thousand, four hundred fifty-seven".